1. Field of the Invention:
The invention relates in general to drive chains, and more specifically to multiple strand roller drive chains for transmitting power from toothed sprockets to an endless belt constructed of toothed links.
2. Description of the Prior Art:
U.S. Pat. No. 3,677,388, which is assigned to the same assignee as the present application, discloses a new and improved drive arrangement for an escalator in which a modular drive unit drives a pair of sprockets. Multiple strand drive chains link the driven sprockets with idler sprockets. An endless belt is driven by drive chains. Each side of the endless belt is constructed of interconnected toothed links. The two sides are interconnected via step axles, to which the escalator steps are attached. The toothed links on each side of the belt engage a driving strand of each multiple strand drive chain, to cause the endless belt to be driven in a loop. Each driving strand includes a plurality of spaced rollers constructed of a resilient material, such as polyurethane. The resilient rollers distribute the load more uniformly between the rollers which are in engagement with the teeth of the toothed links, than rigid rollers. While the load is substantially uniformly distributed between a plurality of rollers when the drive chain is new, the sharing of load becomes increasingly disproportionate as the chain wears. This shortens the useful operating life of the chain because of premature failure of the resilient rollers.